High temperature thermistor composition

ABSTRACT

A high temperature thermistor composition comprising essentially a spinel-type solid solution being formed from a unity in the sum of a molar fraction of at least one oxide selected from the group consisting of magnesium oxide, nickel oxide, cobalt oxide, manganese oxide and zinc oxide and a unity in the sum of a molar fraction of aluminum oxide, chromium oxide, and at least one oxide selected from the group consisting of iron oxide, manganese oxide, cobalt oxide and antimony oxide.

BACKGROUND OF THE INVENTION

This invention relates to a composition for thermistor, and more particularly to a composition for high temperature thermistors.

The conventional thermistors have been used for temperature measurement usually in the range of from room temperature to about 300°C. Such kind of thermistor is of a composition comprising cobalt oxide, manganese oxide, nickel oxide and/or iron oxide.

Recently, a high temperature thermistor which can be operable at a high temperature range up to about 1000°C has been developed. For example, it was disclosed in Japanese Pat. Publication S41-15855/1966 that the thermistors, which consists of the solid solution of SnO₂ -TiO₂ system as the principal component and additive of at least one oxide selected from the group consisting of Sb₂ O₃ and Ta₂ O₃ in the amount of less than 5% by mole, were able to be used in a high temperature up to 1000°C. It was also disclosed in Rev. of Scientific Inst., 40 pp. 544-549 (1969) that the thermistors consisting of ZrO₂ as the principal component and additive of Y₂ O₃ were able to be operable in a high temperature to about 1000°C. Furthermore, it was disclosed in U.S. Pat. No. 3,598,764 (1971) that the thermistors consisting of CeO₂ as the principal component and additive of ZrO₂ in the amount of 2 to 15% by weight were able to be used in a high temperature up to 1000°C.

However, these conventional materials for a high temperature thermistor have inferior and time-dependent characteristics. Particularly, they display unstability in usage on a high temperature under an application of a d.c. voltage.

Recently, a high temperature thermistor which can be used in a working temperature above 300°C has been intensively required. For example, it is desired to be used for a temperature controller, which has the working temperature range of 600°C to 1000°C, of a thermal reactor of a motor car in which an exhausting gas from an engine is reburnt. In such a case, the high temperature thermistors must be used under an application of d.c. voltage, because an electric power source in a motorcar is a d.c. electrical battery.

SUMMARY OF THE INVENTION

It is, therefore, an object of the present invention to provide novel compositions of high temperature thermistors having superior and steady electrical characteristics.

It is another object of the present invention to provide compositions of high temperature thermistors having a high stability of electrical characteristics in load aging under an application of a d.c. voltage.

It is further the object of the present invention to provide a high temperature thermistor composition comprising a spinel-type solid solution and having resistance and B-value which can be widely changed in a working temperature with variation of the amounts of the components of said solid solution.

These objects are achieved by providing a high temperature thermistor composition according to the present invention, which comprises a spinel-type solid solution being formed from a unity in the sum of a molar fraction of at least one oxide selected from the group consisting of magnesium oxide, nickel oxide, cobalt oxide, manganese oxide and zinc oxide and a unity in the sum of a molar fraction of aluminum oxide, chromium oxide, and at least one oxide selected from the group consisting of iron oxide, manganese oxide, cobalt oxide and antimony oxide, wherein said aluminum oxide is in the amount of 0.005 to 0.8 by a molar fraction, said chromium oxide is in the amount of 0.03 to 0.95 by a molar fraction, and said at least one oxide selcted from the group consisting of iron oxide, manganese oxide, cobalt oxide and antimony oxide is in the amount of 0.005 to 0.7 by a molar fraction.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other objects and features and advantages of the present invention will be apparent upon consideration of the following detailed description taken together with the accompanying drawings in which:

FIG. 1 is a schematic view of a high temperature thermistor of the rod type according to the present invention: and

FIG. 2 is a graph showing the temperature dependence of electrical resistivity of a high temperature thermistor of a composition including magnesium oxide, aluminum oxide, chromium and ferric oxide in accordance with the present invention.

DETAILED DESCRIPTION OF THE INVENTION

It has been discovered according to the present invention that a high temperature thermistor showing a high stability of electrical characteristics in load aging under an application of a d.c. voltage is achieved by using a sintered body of a composition consisting essentially of a spinel-type solid solution which is formed from a unity in the sum of a molar fraction of at least one oxide selected from the group consisting of magnesium oxide, nickel oxide, cobalt oxide, manganese oxide and zinc oxide and a unity in the sum of a molar fraction of aluminum oxide, chromium oxide, and at least one oxide selected from the group consisting of iron oxide, manganese oxide, cobalt oxide and antimony oxide.

The preferred composition of a high temperature thermistor according to the present invention is formed from the ternary system of 0.5 to 80 mole percent of MgAl₂ O₄, 3 to 95 mole percent of MgCr₂ O₄, and 0.5 to 70 mole percent of MgFe₂ O₄, wherein Mg can be substituted partially or fully by Ni, Co, Mn and Zn, and also Fe can be substituted partially or fully by Mn, Co and Sb. Although a spinel-type solid solution being formed from the binary system, for example, MgAl₂ O₄ 13 MgCr₂ O₄, MgCr₂ O₄ --MgFe₂ O₄, or MgAl₂ O₄ --NiFe₂ O₄ has inferior and unstable electrial characteristics, a spinel-type solid solution being formed from the ternary system, for example, MgAl₂ O₄ --MgCr₂ O₄ --MgFe₂ O₄, NiAl₂ O₄ --NiCr₂ O₄ --NiFe₂ O₄, or CoAl₂ O₄ --CoCr₂ O₄ --CoMn₂ O₄ makes it possible to obtain a high temperature thermistor characterized by a high stability of electrical characteristics in load aging under an application of a d.c. voltage. Such a spinel-type solid solution as in the ternary system has an advantage that one can choose the desirable resistance and B-value in a working temperature by changing the amount of components of the spinel-type solid solution without changing the kind of said components.

Furthermore, the composition of said high temperatue thermistor can be incorporated with additives of less than 20 molar percent of at least one oxide selected from the group consisting of each component forming said composition of a spinel-type solid solution, that is, MgO, NiO, CoO, MnO, ZnO, Al₂ O₃, Cr₂ O₃, Fe₂ O₃, Mn₂ O₃, Co₂ O₃, and Sb₂ O₃. This incorporation with said additives also facilitates to choose the desirable resistance and B-value in a working temperature.

The compositions of the high temperature thermistor according to the present invention are formed from spinel-type solid solutions having the following chemical formula:

1. Generally, (Mg.sub.[_(p).sbsb.1 _(]Ni).sub.[_(p).sbsb.2 _(]Co).sub.[_(p).sbsb.3 _(]Mn).sub.[_(p).sbsb.4 _(]Zn).sub.[_(p).sbsb.5 _(])) (Al.sub.[ _(x) _(]Cr).sub.[_(y) _(]Fe).sub.[_(z).sbsb.1 _(]Mn).sub.[_(z).sbsb.2 _(]Co).sub.[_(z).sbsb.3 _(]Sb).sub.[_(z).sbsb.4 _(]))₂ O₄ wherein p₁ +p₂ +p₃ +p₄ +p₅ =1, 0≦p_(n) ≦1 (n=1, 2, 3, 4, 5), Z₁ +z₂ +z₃ +z₄ =z, x+y+z=1, 0.005≦x≦0.80, 0.03≦y≦0.95, 0.005≦z≦0.70 and 0≦z_(n) ≦0.70 (n=1, 2, 3, 4);

2. A(Al.sub.[ _(x) _(]Cr).sub.[_(y) _(]B).sub.[_(z) _(]))₂ O₄ wherein A is Mg, Ni, Co, Mn or Zn, B is Fe, Mn, Co or Sb, x is from 0.005 to 0.80, y is from 0.03 to 0.95, z is from 0.005 to 0.70, and x+y+z=1;

3. (Mg.sub.[_(1-p) _(]) A.sub.[_(p) _(]) ) (Al.sub.[ _(x) _(]) Cr.sub.[_(y) _(]) B.sub.[_(z) _(]) )₂ O₄ wherein A is Ni, Co, Mn or Zn, B is Fe, Mn, Co or Sb, and p is from 0.001 to 0.999. This composition corresponds to Mg(Al.sub.[ _(x) _(]Cr).sub.[_(y) _(]B).sub.[₃ _(])) ₂ O₄ (which is one of the above No. (2) compositions) where Mg is partially substituted by Ni, Co, Mn or Zn; x, y and z are as defined in (2) above.

4. (Ni.sub.[_(1-p) _(]A).sub.[_(p) _(])) (Al.sub.[ _(x) _(]Cr).sub.[_(y) _(]B).sub.[_(z) _(]))₂ O₄ wherein A is Co, Mn or Zn, B is Fe, Mn, Co or Sb, and p is from 0.001 to 0.999; x, y and z are as defined in (2) above;

5. (Co.sub.[_(1-p) _(]A) .sub.[_(p) _(]))(Al.sub.[ _(x) _(]Cr).sub.[_(y) _(]) B.sub.[_(z) _(]))₂ O₄ wherein A is Mn or Zn, B is Fe, Mn, Co or Sb, and p is from 0.001 to 0.999; x, y and z are as defined in (2) above.

6. (Zn.sub.[_(1-p) _(]Mn).sub.[_(p) _(])) (Al.sub.[ _(x) _(]Cr).sub.[_(y) _(]B).sub.[_(z) _(]))₂ O₄ wherein B is Fe, Mn, Co or Sb, and p is from 0.001 to 0.999; x, y and z are as defined in (2) above;

7. (Mg.sub.[_(1-p-q) _(]Ni).sub.[ _(p) _(]A).sub.[_(q) _(]) ) (Al.sub.[ _(x) _(]Cr).sub.[_(y) _(]B).sub.[ _(z) _(]))₂ O₄ wherein A is Co, Mn or Zn, B is Fe, Mn, Co or Sb, p is from 0.001 to 0.999, q is from 0.0005 to 0.998, and p+q<1. This composition corresponds to (Mg.sub.[_(1-p) _(]Ni).sub.[_(p) _(])) (Al.sub.[ _(x) _(]) Cr.sub.[_(y) _(]B).sub.[_(z) _(]))₂ O₄ (which is one of the above No. (3) compositions) where Ni is partially substituted by Co, Mn or Zn; x, y and z are as defined in (2) above;

8. (Ni.sub.[_(1-p-q) _(]Co).sub.[_(p) _(]A).sub.[_(q) _(])) (Al.sub.[ _(x) _(]Cr).sub.[_(y) _(]B).sub.[_(z) _(])).sub. 2 O₄ wherein A is Mn or Zn, B is Fe, Mn, Co or Sb, p is from 0.001 to 0.999, q is from 0.0005 to 0.998, and p+q<1; x, z and z are as defined in (2) above;

9. A(Al.sub.[ _(x) _(]Cr).sub.[_(y) _(]Fe).sub.[_(z-w) _(]B).sub.[_(w) _(])).sub. 2 O₄ wherein A is Mg, Ni, Co, Mn or Zn, B is Mn, Co or Sb, and w is from 0.001 to 0.699. This composition corresponds to A (Al.sub.[ _(x) _(]Cr).sub.[_(y) _(]Fe).sub.[_(z) _(]) )₂ O₄ which is one of the above No. 2 compositions where Fe is partially substituted by Mn, Co or Sb). X, y and z are as defined in (2) above;

10. (Mg.sub.[_(1-p) _(]A).sub.[_(p) _(])) (Al.sub.[ _(x) _(]Cr).sub.[_(y) _(]Fe).sub.[_(z-w) _(]B).sub.[_(w) _(])).sub. 2 O₄ wherein A is Ni, Co, Mn or Zn, B is Mn, Co or Sb, p is from 0.001 to 0.999, w is from 0.001 to 0.699; and x, y and z are as defined in (2) above;

11. (Ni.sub.[_(1-p) _(]A).sub.[_(p) _(])) (Al.sub.[ _(x) _(]Cr).sub.[_(y) _(]Fe).sub.[_(z-w) _(]B).sub.[_(w) _(])).sub. 2 O₄ wherein A is Co, Mn or Zn, B is Mn, Co or Sb, p is from 0.001 to 0.999, and w is from 0.001 to 0.699; x, y and z are as defined in (2) above;

12. (Co.sub.[_(1-p) _(]A).sub.[_(p) _(]) ) (Al.sub.[ _(x) _(]Cr).sub.[_(y) _(]Fe).sub.[_(z-w) _(]B).sub.[_(w) _(])).sub. 2 O₄ wherein A is Mn or Zn, B is Mn, Co or Sb, p is from 0.001 to 0.999, w is from 0.001 to 0.699 and x, y and z are as defined in (2) above;

13. (Zn.sub.[_(1-p) _(]Mn).sub.[_(p) _(]) ) (Al.sub.[ _(x) _(]Cr).sub.[_(y) _(]Fe).sub.[_(z-w) _(]B).sub.[_(w) _(])).sub. 2 O₄ wherein B is Mn, Co or Sb, p is from 0.001 to 0.999, w is from 0.001 to 0.699 and x, y and z are as defined in (2) above;

14. (Mg.sub.[_(1-p-q) _(]Ni).sub.[_(p) _(]A).sub.[_(q) _(])) (Al.sub.[ _(x) _(]Cr).sub.[_(y) _(]Fe).sub.[_(z-w) _(]B).sub.[_(w) _(])).sub. 2 O₄ wherein A is Co, Mn or Zn, B is Mn, Co or Sb, p is from 0.001 to 0.999, q is from 0.0005 to 0.998, p+q<1, w is from 0.001 to 0.699 and x, y and z are as defined in (2) above;

15. (Ni.sub.[_(1-p-q) _(]C).sub.[_(p) _(]A).sub.[_(q) _(])) (Al.sub.[ _(x) _(]Cr).sub.[_(y) _(]Fe).sub.[_(z-w) _(]B).sub.[_(w) _(]))₂ O₄ wherein A is Mn or Zn, B is Mn, Co or Sb, p is from 0.001 to 0.999, q is from 0.0005 to 0.998, p+q<1, and w is from 0.001 to 0.699, and x, y and z are as defined in (2) above.

Preferable compositions according to the present invention are:

16. More than 80 molar percent of a spinel-type solid solution in a chemical formula of A(Al.sub.[ _(x) _(]Cr).sub.[_(y) _(]B).sub.[_(z) _(])).sub. 2 O₄ and less than 20 molar percent of an oxide of the chemical formula AO, wherein A is Mg, Ni, Co, Mn or Zn, B is Fe, Mn, Co or Sb, 0.005≦x≦0.80, 0.03≦y≦0.95, 0.005≦z≦0.70, and x+y+z=1.

17. More than 80 molar percent of a spinel type solid solution in a chemical formula A(Al.sub.[ _(x) _(]Cr).sub.[_(y) _(]B).sub.[_(z) _(])).sub. 2 O₄ and less than 20 molar percent in the sum of the amounts of Al.sub. 2 O₃, Cr₂ O₃ and [B]₂ O₃ which are in a molar fraction of x, y and z, respectively, wherein A is Mg, Ni, Co, Mn or Zn, and B is Fe, Mn, Co or Sb, 0.005≦x≦0.80, 0.03≦y≦0.95, 0.005≦z≦0.70, and x+y+z=1.

18. More than 80 molar percent of a spinel-type solid solution in a chemical formula of (Mg.sub.[_(1-p) _(]A).sub.[_(p) _(])) (Al.sub.[ _(x) _(]Cr).sub.[_(y) _(]B).sub.[_(z) _(]))₂ O₄ and less than 20 molar percent in the sum of the amounts of MgO and AO which are in a molar fraction of 1-p and p, respectively, wherein A is Mg, Ni, Co, Mn or Zn, B is Fe, Mn, Co or Sb, p is from 0.001 to 0.999, 0.005≦x≦0.80, 0.03≦y≦0.95, 0.005≦z≦0.70, and x+y+z=1.

19. More than 80 molar percent of a spinel-type solid solution in a chemical formula of (Mg.sub.[_(1-p) _(]A).sub.[_(p) _(])) Al.sub.[ _(x) _(]Cr).sub.[_(y) _(]B).sub.[_(z) _(]))₂ O₄ and less than 20 molar percent in the sum of the amounts of Al.sub. 2 O₃, Cr₂ O₃ and [B]₂ O₃ which are in a molar fraction of x, y and z, respectively, wherein A is Mg, Ni, Co, Mn or Zn, B is Fe, Mn, Co, or Sb, p is from 0.001 to 0.999, 0.005≦x≦0.80, 0.03≦y≦0.95, 0.005≦z≦0.70, and x+y+z=1.

The manufacturing process for producing the material of the invention and preparing high-temperature thermistors therefrom is as follows. The starting mixture of MgO, NiO, CoO, MnCO₃ (is converted to MnO by heating), ZnO, Al₂ O₃, Cr₂ O₃, Fe₂ O₃, MnO₂ and Sb₂ O₃ taken in the appropriate proportions is thoroughly mixed in the presence of alcohol in an agate drum, and after being mixed the mixture is prefired at a temperture of 1100°C to 1500°C for a period of 1 to 5 hours. The prefired mixture is then subjected to wet grinding in an agate drum for 3 to 24 hours. And then, the prefired powders are dried, mixed with pure water by 6% in weight and granulated. After that, the powders are pressed into a form of rod of 2 mm in diameter and 4 mm in thickness, with inserting two lead wires of platinum of 0.3 mm in diameter into the rod-shaped powder compact, as shown in FIG. 1. In next, the pressed rods with Pt leads are sintered at a temperture ranging from 1400° to 1700°C in air for a period of 1 to 5 hours. In FIG. 1, the reference numeral 1001 designates a sintered body of a high temperature thermistor having a composition according to the invention. A pair of electrodes 1002, which are made of platinum, are set to the powder compact of the high temperature thermistor material at a pressing process, as described above, before sintering. The outside parts of the elctrodes 1002 are used also as the lead wires.

For the obtained rods of high temperature thermistors, the resistance was measured in a temperature range from 20°C to 1400°C, and B-values was calculated from the following equation: ##EQU1## where R₁ is electrical resitance at T₁ °K and R₂ is electrical resistance at T₂ °K. The constant B is named a B-value, as described above. Furthermore, aging tests, which are important for practical use, were examined. The resistance of said high temperature thermistors was masured with the lapse of time at a soaking temperature of 1000°C under a continuous application of a d.c. voltage of 6V. Resistance deviating in an aging test is defined by the term of ##EQU2## where R_(o) is an initial resistance in an aging test and R_(t) is a resistance in the lapse of the time (t).

EXAMPLE 1

Mixtures of magnsium oxide, alumina oxide, chromium oxide and ferric oxide in the composition listed in Table 1(a) were thoroughly mixed in the presence of alcohol in an agate drum for 5 hours.

                  Table 1(a)                                                       ______________________________________                                               Compositions (mol ratio)                                                 Sample                   Prefiring Sintering                                   No.   MgO    Al.sub.2 O.sub.3                                                                       Cr.sub.2 O.sub.3                                                                     Fe.sub.2 O.sub.3                                                                     temperature                                                                            temperature                                                            (°C)                                                                            (°C)                           ______________________________________                                         1     1.00   0.80     0.005                                                                                0.195                                                                               1350    1650                                  2     1.00   0.80     0.195                                                                                0.005                                                                               1400    1700                                  3     1.00    0.005  0.95   0.045                                                                               1300    1650                                  4     1.00    0.045  0.95   0.005                                                                               1350    1700                                  5     1.00    0.005   0.295                                                                               0.70  1150    1520                                  6     1.00    0.295   0.005                                                                               0.70  1150    1520                                  7     1.00   0.30    0.50  0.20  1250    1650                                  8     1.00   0.05    0.50  0.45  1200    1600                                  9     1.00   0.50    0.25  0.25  1250    1620                                  10    1.00   0.02    0.90  0.08  1300    1650                                  11    1.00   0.15    0.50  0.35  1200    1620                                  12    1.00   0.40    0.40  0.20  1250    1650                                  ______________________________________                                    

The mixtures were dried and pressed into cakes at a pressure of 400kg/cm². The cakes were prefired at each temperature shown in Table 1(a) for 3 hours. The prefired cakes were wet ground in an agate drum for 5 hours.

And then, the ground powders were dried, mixed with a pure water by 6 weight % and granulated. After that, the powders were pressed into a form of rod of 2 mm in diameter and 4 mm in thickness, with inserting two lead wires of platinum of 0.3mm in diameter were inserted into the rod-type powder compact. The pressed rods with P_(t) leads were sintered in air at each temperature given in Table 1(a) for 3 hours. The resultant rods have a temperature dependence of electrical resistance as shown in FIG. 2, wherein the sample Nos. correspond to the compositons listed in Table 1(a). For each sample, the resistances at temperatures of 600°C and 1000°C, B-value between both temperatures of 600°C and 1000°C, and resistance deviation in ageing for 100 hours and 1000 hours are given in Table 1(b).

                                      Table 1(b)                                   __________________________________________________________________________     Sample                                                                             Resistance(Ω)                                                                               Resistance deviation                                                           R.sub.t -R.sub.o                                        No.               B-value  × 100  (%)                                                           R.sub.o                                                     at 600°C                                                                       at 1000°C                                                                           in the lapse                                                                           in the lapse                                                           of 100 hrs.                                                                            of 100 hrs.                                     __________________________________________________________________________     1   9.8 × 10.sup.4                                                                  2.3 × 10.sup.3                                                                  10500                                                                               + 86    + 530                                           2   2.8 × 10.sup.7                                                                  9.9 × 10.sup.4                                                                  15700                                                                               + 78    + 365                                           3   6.7 × 10                                                                        1.6 × 10                                                                        4000 + 9.4   + 99                                            4   6.0 × 10                                                                        2.4 × 10                                                                        2600 + 85    + 510                                           5   2.1 × 10.sup.2                                                                  8.2    9000 + 37    + 110                                           6   4.5 × 10.sup.2                                                                  4.4 × 10                                                                        6500 + 28    + 82                                            7   3.3 × 10.sup.5                                                                  2.2 × 10.sup.3                                                                  13900                                                                               + 1.3   +  8.0                                          8   4.3 × 10.sup.3                                                                  1.3 × 10.sup.2                                                                  9700 + 5.9   + 29                                            9   6.0 × 10.sup.4                                                                  2.0 × 10.sup.3                                                                  9500 + 2.5   + 13                                            10  7.2 × 10                                                                        1.8 × 10                                                                        3900 + 14    + 105                                           11  3.3 × 10.sup.4                                                                  5.4 × 10.sup.2                                                                  11400                                                                               + 1.7   + 9.7                                           12  7.2 × 10.sup.4                                                                  1.7 × 10.sup.3                                                                  10400                                                                               - 0.4   + 3.9                                           __________________________________________________________________________

EXAMPLE 2

High temperature thermistors of compositons listed in Table 2(a) were prepared in a manner similar to that of Example 1.

                  Table 2(a)                                                       ______________________________________                                               Compositions (ingredient)                                                                         Prefiring Sintering                                   Sample                                                                               (mol ratio)        temperature                                                                              temperature                                 No.   1.00   0.30    0.50  0.20  (°C)                                                                            (°C)                           ______________________________________                                         13    MgO    Al.sub.2 O.sub.3                                                                       Cr.sub.2 O.sub.3                                                                     Mn.sub.2 O.sub.3                                                                     1250    1650                                  14    "      "       "     Co.sub.2 O.sub.3                                                                     "       "                                     15    "      "       "     Sb.sub.2 O.sub.3                                                                     "       "                                     16    NiO    "       "     Fe.sub.2 O.sub.3                                                                     "       1620                                  17    "      "       "     Mn.sub.2 O.sub.3                                                                     "       "                                     18    "      "       "     Co.sub.2 O.sub.3                                                                     "       "                                     19    "      "       "     Sb.sub.2 O.sub.3                                                                     "       "                                     20    CoO    "       "     Fe.sub.2 O.sub.3                                                                     "       1640                                  21    "      "       "     Mn.sub.2 O.sub.3                                                                     "       "                                     22    "      "       "     Sb.sub.2 O.sub.3                                                                     "       "                                     23    MnO    "       "     Fe.sub.2 O.sub.3                                                                     "       1620                                  24    "      "       "     Co.sub.2 O.sub.3                                                                     "       "                                     25    "      "       "     Sb.sub.2 O.sub.3                                                                     "       "                                     26    ZnO    "       "     Fe.sub.2 O.sub.3                                                                     "       1640                                  27    "      "       "     Mn.sub.2 O.sub.3                                                                     "       "                                     28    "      "       "     Co.sub.2 O.sub.3                                                                     "       "                                     29    "      "       "     Sb.sub.2 O.sub.3                                                                     "       "                                     ______________________________________                                    

For each sample of the resultant high temperature thermistors, the measured resistances at temperatues of 600°C and 1000°C, B-value between both temperatures of 600°C and 1000°C, and resistance deviation in aging for 100 hours and 1000 hours are given in Table 2(b).

                                      Table 2(b)                                   __________________________________________________________________________     Sample                                                                             Resistance (Ω)                                                                              Resistance deviation                                                           R.sub.t -R.sub.o                                                          B-value  × 100%                                                               R.sub.o                                                 No.                    in the lapse                                                                           in the lapse                                        at 600°C                                                                       at 1000°C                                                                           of 100 hrs                                                                             of 1000 hrs                                     __________________________________________________________________________     13  1.2 × 10.sup.4                                                                  8.0 × 10.sup.2                                                                  7500 2.6     13.5                                            14  4.9 × 10.sup.5                                                                  2.4 × 10.sup.3                                                                  14800                                                                               1.8     10.6                                            15  5.5 × 10.sup.4                                                                  1.1 × 10.sup.3                                                                  10900                                                                               3.9     25                                              16  3.2 × 10.sup.4                                                                  3.2 × 10.sup.2                                                                  12800                                                                               1.8     5.0                                             17  4.1 × 10.sup.3                                                                  1.4 × 10.sup.2                                                                  9400 3.4     18                                              18  5.1 × 10.sup.4                                                                  3.6 × 10.sup.2                                                                  13800                                                                               2.1     11.5                                            19  1.8 × 10.sup.4                                                                  4.1 × 10.sup.2                                                                  10500                                                                               5.3     40                                              20  1.1 × 10.sup.4                                                                  4.1 × 10.sup.2                                                                  9100 3.6     21                                              21  3.4 × 10.sup.3                                                                  1.7 × 10.sup.2                                                                  8300 6.0     52                                              22  7.6 × 10.sup.3                                                                  4.2 × 10.sup.2                                                                  8000 7.2     67                                              23  9.3 × 10.sup.4                                                                  2.0 × 10.sup.3                                                                  10700                                                                               4.7     38                                              24  1.2 × 10.sup.5                                                                  2.2 × 10.sup.3                                                                  11100                                                                               8.2     71                                              25  3.5 × 10.sup.4                                                                  4.0 × 10.sup.3                                                                  6000 5.1     46                                              26  1.3 × 10.sup.3                                                                  1.6 × 10.sup.2                                                                  5800 4.2     34                                              27  4.0 × 10.sup.2                                                                  8.5 × 10                                                                        4300 5.3     45                                              28  2.6 × 10.sup.3                                                                  1.8 × 10.sup.2                                                                  7400 8.5     66                                              29  1.0 × 10.sup.3                                                                  1.5 × 10.sup.2                                                                  5300 4.8     42                                              __________________________________________________________________________

EXAMPLE 3

High temperature thermistors of compositions listed in Table 3(a) were prepared in a manner similar to that of Example 1.

                                      Table 3(a)                                   __________________________________________________________________________     Sample                                                                             Compositions (mol ratio) Prefiring                                                                             Sintering                                  No. MgO  NiO  Al.sub.2 O.sub.3                                                                    Cr.sub.2 O.sub.3                                                                    Fe.sub.2 O.sub.3                                                                    temperature                                                                           temperature                                                             (°C)                                                                           (°C)                                __________________________________________________________________________     30   0.999                                                                               0.001                                                                              0.30 0.50 0.20 1250   1650                                       31  0.70 0.30 0.30 0.50 0.20 1250   1650                                       32  0.20 0.80 0.30 0.50 0.20 1250   1620                                       33   0.001                                                                               0.999                                                                              0.30 0.50 0.20 1250   1620                                       34  0.50 0.50 0.80  0.005                                                                               0.195                                                                              1300   1620                                       35  0.50 0.50 0.50  0.495                                                                               0.005                                                                              1350   1620                                       36  0.50 0.50 0.30 0.50 0.20 1250   1620                                       37  0.50 0.50 0.10 0.20 0.70 1150   1550                                       38  0.50 0.50  0.005                                                                              0.95  0.045                                                                              1300   1650                                       __________________________________________________________________________

For each sample of the resultant high temperature thermistors, the measured electrical characteristics are given in Table 3(b).

                                      Table 3(b)                                   __________________________________________________________________________     Sample                                                                             Resistance (Ω)                                                                              Resistance deviation                                                           R.sub.t -R.sub.o                                                          B-value  × 100 %                                                              R.sub.o                                                 No.                    in the lapse                                                                           in the lapse                                        at 600°C                                                                       at 1000°C                                                                           of 100 hrs                                                                             of 1000 hrs                                     __________________________________________________________________________     30  3.6 × 10.sup.5                                                                  2.4 × 10.sup.3                                                                  13900                                                                               6.4     45                                              31  3.5 × 10.sup.4                                                                  6.8 × 10.sup.2                                                                  11000                                                                               2.1     18                                              32  5.9 × 10.sup.3                                                                  1.8 × 10.sup.2                                                                  9700 0.8     4.1                                             33  3.1 × 10.sup.4                                                                  3.2 × 10.sup.2                                                                  12700                                                                               1.9     5.1                                             34  1.2 × 10.sup.6                                                                  2.7 × 10.sup.4                                                                  10500                                                                               22      140                                             35  3.5 × 10.sup.3                                                                  2.7 × 10.sup.2                                                                  7100 15      79                                              36  5.9 × 10.sup.3                                                                  2.0 × 10.sup.2                                                                  9400 1.1     9.4                                             37  6.6 × 10                                                                        1.9 × 10                                                                        3500 39      125                                             38  8.4 ×  10                                                                       4.2 × 10                                                                        1900 98      720                                             __________________________________________________________________________

EXAMPLE 4

High temperature thermistors of compositions listed in Table 4(a) were prepared in a manner similar to that of Example 1.

For each sample of the resultant high temperature thermistors, the measured electrical characteristics are given in Table 4(b).

                                      Table 4(a)                                   __________________________________________________________________________         Compositions (ingredient)                                                                             Prefiring                                                                             Sintering                                    Sample                                                                             (mol ratio)            temperature                                                                           temperature                                  No. 0.5 0.5 0.3  0.5  0.2  (°C)                                                                           (°C)                                  __________________________________________________________________________     39  MgO CoO Al.sub.2 O.sub.3                                                                    Cr.sub.2 O.sub.3                                                                    Fe.sub.2 O.sub.3                                                                    1250   1650                                         40  "   "   "    "    Mn.sub.2 O.sub.3                                                                    "      "                                            41  "   "   "    "    Sb.sub.2 O.sub.3                                                                    "      "                                            42  "   MnO "    "    Fe.sub.2 O.sub.3                                                                    "      1640                                         43  "   "   "    "    Co.sub.2 O.sub.3                                                                    "      "                                            44  "   "   "    "    Sb.sub.2 O.sub.3                                                                    "      "                                            45  "   ZnO "    "    Mn.sub.2 C.sub.3                                                                    "      1650                                         46  "   "   "    "    Co.sub.2 O.sub.3                                                                    "      "                                            47  "   "   "    "    Sb.sub.2 O.sub.3                                                                    "      "                                            48  NiO CoO "    "    Fe.sub.2 O.sub.3                                                                    "      1630                                         49  "   "   "    "    Mn.sub.2 O.sub.3                                                                    "      "                                            50  "   "   "    "    Co.sub.2 O.sub.3                                                                    "      "                                            51  "   "   "    "    Sb.sub.2 O.sub.3                                                                    "      "                                            52  "   MnO "    "    Fe.sub.2 O.sub.3                                                                    "      1620                                         53  "   "   "    "    Co.sub.2 O.sub.3                                                                    "      "                                            54  "   "   "    "    Sb.sub.2 O.sub.3                                                                    "      "                                            55  "   ZnO "    "    Fe.sub.2 O.sub.3                                                                    "      1630                                         56  "   "   "    "    Mn.sub.2 O.sub.3                                                                    "      "                                            57  "   "   "    "    Co.sub.2 O.sub.3                                                                    "      "                                            58  "   "   "    "    Sb.sub.2 O.sub.3                                                                    "      "                                            59  CoO MnO "    "    Fe.sub.2 O.sub.3                                                                    "      "                                            60  "   "   "    "    Co.sub.2 O.sub.3                                                                    "      "                                            61  "   "   "    "    Sb.sub.2 O.sub.3                                                                    "      "                                            62  "   ZnO "    "    Fe.sub.2 O.sub.3                                                                    "      1640                                         63  "   "   "    "    Mn.sub.2 O.sub.3                                                                    "      "                                            64  "   "   "    "    Sb.sub.2 O.sub.3                                                                    "      "                                            65  ZnO MnO "    "    Fe.sub.2 O.sub.3                                                                    "      1630                                         66  "   "   "    "    Mn.sub.2 O.sub.3                                                                    "      "                                            67  "   "   "    "    Co.sub.2 O.sub.3                                                                    "      "                                            68  "   "   "    "    Sb.sub. O.sub.3                                                                     "      "                                            __________________________________________________________________________

                                      Table 4(b)                                   __________________________________________________________________________     Sample                                                                             Resistance (Ω)                                                                              Resistance deviation                                                           R.sub.t -R.sub.o                                        No.               B-value  × 100 (%)                                                            R.sub.o                                                 at 600°C                                                                           at 1000°C                                                                           in the lapse                                                                           in the lapse                                                           of 100 hrs.                                                                            of 1000 hrs.                                    __________________________________________________________________________     39  4.2 × 10.sup.3                                                                  2.1 × 10.sup.2                                                                  8300 1.1     6.8                                             40  2.0 × 10.sup.3                                                                  16 × 10.sup.2                                                                   7000 5.1     29                                              41  3.9 × 10.sup.3                                                                  2.0 × 10.sup.2                                                                  8300 2.5     16                                              42  1.8 × 10.sup.4                                                                  5.7 × 10.sup.2                                                                  9600 1.8     8.7                                             43  1.5 × 10.sup.4                                                                  4.5 × 10.sup.2                                                                  9700 1.4     6.5                                             44  1.4 × 10.sup.4                                                                  4.7 × 10.sup.2                                                                  9400 3.2     21                                              45  7.9 × 10.sup.2                                                                  9.8 × 10                                                                        5800 6.7     47                                              46  1.5 × 10.sup.3                                                                  1.5 × 10.sup.2                                                                  6400 3.1     24                                              47  1.1 × 10.sup.3                                                                  1.5 × 10.sup.2                                                                  5500 3.6     29                                              48  2.8 × 10.sup.3                                                                  1.8 × 10.sup.2                                                                  7600 1.3     6.5                                             49  1.6 × 10.sup.3                                                                  1.4 × 10.sup.2                                                                  6800 4.8     27                                              50  5.6 × 10.sup.3                                                                  2.6 × 10.sup.2                                                                  8500 1.9     9.6                                             51  3.1 × 10.sup.3                                                                  1.7 × 10.sup.2                                                                  8100 2.6     18                                              52  9.3 × 10.sup.3                                                                  3.0 × 10.sup.2                                                                  9500 2.3     12                                              53  9.0 × 10.sup.3                                                                  2.7 × 10.sup.2                                                                  9700 2.0     9.9                                             54  9.1 × 10.sup.3                                                                  2.9 × 10.sup.2                                                                  9600 2.6     20                                              55  1.0 × 10.sup.3                                                                  1.1 ×10.sup.2                                                                   6100 4.1     27                                              56  6.1 × 10.sup.2                                                                  9.1 × 10                                                                        5300 5.3     35                                              57  9.8 × 10.sup.2                                                                  1.1 × 10.sup.2                                                                  6100 3.7     22                                              58  9.2 × 10.sup.2                                                                  1.2 × 10.sup.2                                                                  5700 4.0     26                                              59  1.1 × 10.sup.4                                                                  4.1 × 10.sup.2                                                                  9100 2.9     23                                              60  1.3 × 10.sup.4                                                                  4.0 ×10.sup.2                                                                   9700 1.7     8.8                                             61  9.0 × 10.sup.3                                                                  3.2 ×  10.sup.2                                                                 9300 4.3     41                                              62  9.8 × 10.sup.2                                                                  1.0 × 10.sup.2                                                                  6300 4.2     28                                              63  5.9 × 10.sup.2                                                                  9.0 × 10                                                                        5200 5.5     37                                              64  9.1 × 10.sup.2                                                                  1.2 × 10.sup.2                                                                  5600 4.2     29                                              65  2.8 × 10.sup.3                                                                  2.6 × 10.sup.2                                                                  6600 6.4     42                                              66  1.5 × 10.sup.3                                                                  2.4 × 10.sup.2                                                                  5100 8.9     76                                              67  2.1 × 10.sup.3                                                                  1.5 × 10.sup.2                                                                  7300 3.6     28                                              68  1.9 × 10.sup.3                                                                  1.9 × 10.sup.2                                                                  6400 5.8     37                                              __________________________________________________________________________

EXAMPLE 5

High temperature thermistors of compositions listed in Table 5(a) were prepared in a manner similar to that of Example 1.

For each sample of the resultant thermistors, the measured electrical characteristics are given in Table 5(b).

                                      Table 5(a)                                   __________________________________________________________________________         Compositions (ingredient)  Prefiring                                                                             Sintering                                Sample                                                                             (mol ratio)                temperature                                                                           temperature                              No. 0.4 0.3 0.3 0.3  0.5  0.2  (°C)                                                                           (°C)                              __________________________________________________________________________     69  MgO NiO CoO Al.sub.2 O.sub.3                                                                    Cr.sub.2 O.sub.3                                                                    Fe.sub.2 O.sub.3                                                                    1250   1640                                     70  "   "   "   "    "    Mn.sub.2 O.sub.3                                                                    "      "                                        71  "   "   "   "    "    Sb.sub.2 O.sub.3                                                                    "      "                                        72  "   "   MnO "    "    Fe.sub.2 O.sub.3                                                                    "      1630                                     73  "   "   "   "    "    CO.sub.2 O.sub.3                                                                    "      "                                        74  "   "   "   "    "    Sb.sub.2 O.sub.3                                                                    "      "                                        75  "   "   ZnO "    "    Fe.sub.2 O.sub.3                                                                    "      1640                                     76  "   "   "   "    "    Mn.sub.2 O.sub.3                                                                    "      "                                        77  "   "   "   "    "    CO.sub.2 O.sub.3                                                                    "      "                                        78  "   "   "   "    "    Sb.sub.2 O.sub.3                                                                    "      "                                        79  NiO CoO MnO "    "    Fe.sub.2 O.sub.3                                                                    "      1620                                     80  "   "   "   "    "    Sb.sub.2 O.sub.3                                                                    "      "                                        81  "   "   ZnO "    "    Fe.sub.2 O.sub.3                                                                    "      1630                                     82  "   "   "   "    "    Mn.sub.2 O.sub.3                                                                    "      "                                        83  "   "   "   "    "    CO.sub.2 O.sub.3                                                                    "      "                                        84  "   "   "   "    "    Sb.sub.2 O.sub.3                                                                    "      "                                        __________________________________________________________________________

                                      Table 5(b)                                   __________________________________________________________________________     Sample                                                                             Resistance (Ω)                                                                              Resistance deviation                                                           R.sub.t -R.sub.o                                                          B-value  × 100 (%)                                                            R.sub.o                                                 No. at 600°C                                                                       at 1000°C                                                                           in the lapse                                                                           in the lapse                                                           of 100 hrs                                                                             of 1000 hrs                                     __________________________________________________________________________     69  5.0 × 10.sup.3                                                                  2.0 × 10.sup.2                                                                  8900 1.0     8.2                                             70  2.2 × 10.sup.3                                                                  1.1 × 10.sup.2                                                                  8300 1.3     9.5                                             71  4.7 × 10.sup.3                                                                  1.9 × 10.sup.2                                                                  8900 1.3     8.7                                             72  9.0 × 10.sup.3                                                                  3.5 × 10.sup.2                                                                  9000 1.6     9.0                                             73  8.2 × 10.sup.3                                                                  2.7 × 10.sup.2                                                                  9500 1.4     7.9                                             74  8.0 × 10.sup.3                                                                  3.2 × 10.sup.2                                                                  8900 2.1     12                                              75  3.2 × 10.sup.3                                                                  1.8 × 10.sup.2                                                                  8000 2.7     21                                              76  9.5 × 10.sup.2                                                                  1.4 × 10.sup.2                                                                  5300 4.2     36                                              77  3.1 × 10.sup.3                                                                  1.5 ×  10.sup.2                                                                 8400 1.8     8.3                                             78  1.3 × 10.sup.3                                                                  1.6 ×10.sup.2                                                                   5800 3.5     28                                              79  5.4 × 10.sup.3                                                                  2.4 × .sup.2                                                                    8700 1.8     9.0                                             80  4.1 × 10 .sup.3                                                                 2.2 × 10.sup.2                                                                  8100 2.9     24                                              81  1.7 × 10.sup.3                                                                  1.4 × 10.sup.2                                                                  6900 2.8     19                                              82  8.3 × 10.sup.2                                                                  1.0 × 10.sup.2                                                                  5900 4.6     40                                              83  1.7 × 10.sup.3                                                                  1.2 × 10.sup.2                                                                  7300 2.3     14                                              84  1.2 × 10.sup.3                                                                  1.1 × 10.sup.2                                                                  6600 2.7     22                                              __________________________________________________________________________

EXAMPLE 6

High temperature thermistors of compositions listed in Table 6(a) were prepared in a manner similar to that of Example 1.

For each sample of the resultant thermistors, the measured electrical characteristics are given in Table 6(b).

                                      Table 6(a)                                   __________________________________________________________________________         Compositions (ingredient)                                                                              Prefiring                                                                             Sintering                                   Sample                                                                             (mol ratio              temperature                                                                           temperature                                 No. 1.0 0.3  0.5  0.1  0.1  (°C)                                                                           (°C)                                 __________________________________________________________________________     85  MgO Al.sub.2 O.sub.3                                                                    Cr.sub.2 O.sub.3                                                                    Fe.sub.2 O.sub.3                                                                    Mn.sub.2 O.sub.3                                                                    1250   1650                                        86  "   "    "    "    Co.sub.2 O.sub.3                                                                    "      "                                           87  "   "    "    "    Sb.sub.2 O.sub.3                                                                    "      "                                           88  NiO "    "    "    Mn.sub.2 O.sub.3                                                                    "      1620                                        89  "   "    "    "    Co.sub.2 O.sub.3                                                                    "      "                                           90  "   "    "    "    Sb.sub.2 O.sub.3                                                                    "      "                                           91  CoO "    "    "    Mn.sub.2 O.sub.3                                                                    "      1040                                        92  "   "    "    "    Sb.sub.2 O.sub.3                                                                    "      "                                           93  MnO "    "    "    Co.sub.2 O.sub.3                                                                    "      1620                                        94  "   "    "    "    Sb.sub.2 O.sub.3                                                                    "      "                                           __________________________________________________________________________

                                      Table 6(b)                                   __________________________________________________________________________     Sample                                                                             Resistance (Ω)                                                                              Resistance deviation                                                           R.sub.t -R.sub.o                                                          B-value  × 100 (%)                                                            R.sub.o                                                 No. at 600°C                                                                       at 1000°C                                                                           in the lapse                                                                           in the lapse                                                           of 100 hrs                                                                             of 1000 hrs                                     __________________________________________________________________________     85  5.4 × 10.sup.4                                                                  1.4 × 10.sup.3                                                                  10100                                                                               1.8     10.4                                            86  4.1 × 10.sup.5                                                                  4.2 × 10.sup.3                                                                  12700 1.5                                                                           9.1                                                     87  1.6 × 10.sup.5                                                                  1.7 × 10.sup.3                                                                  12600                                                                               2.5     16                                              88  1.1 × 10.sup.4                                                                  2.3 × 10.sup.2                                                                  10700                                                                               2.7     12                                              89  4.2 × 10.sup.4                                                                  3.4 × 10.sup.2                                                                  13400                                                                               1.9     7.7                                             90  2.5 × 10.sup.4                                                                  3.8 × 10.sup.2                                                                  11600                                                                               3.7     24                                              91  6.0 × 10.sup.3                                                                  2.8 × 10.sup.2                                                                   8500                                                                               5.2     36                                              92  8.7 × 10.sup.3                                                                  4.2 × 10.sup.2                                                                    8400                                                                              5.5     43                                              93  1.1 × 10.sup.5                                                                  2.1 × 10.sup.3                                                                  11000                                                                               6.1     47                                              94  5.8 × 10 .sup.4                                                                 3.1 × 10.sup.3                                                                   8100                                                                               4.8     42                                              __________________________________________________________________________

EXAMPLE 7

High temperture thermistors of compositions listed in Table 7(a) were prepared in a manner similar to that of Example 1.

For each sample of the resultant thermistors, the measured electrical characteristics are given in Table 7(b).

                                      Table 7(a)                                   __________________________________________________________________________         Compositions (ingredient)   Prefiring                                                                             Sintering                               Sample                                                                             (mol ratio)                 temperature                                                                           temperature                             No. 0.5 0.5 0.3  0.4  0.15 0.15 (°C)                                                                           (°C)                             __________________________________________________________________________     95  MgO NiO Al.sub.2 O.sub.3                                                                    Cr.sub.2 O.sub.3                                                                    Fe.sub.2 O.sub.3                                                                    Mn.sub.2 O.sub.3                                                                    1250   1620                                    96  "   "   "    "    "    Co.sub.2 O.sub.3                                                                    "      "                                       97  "   "   "    "    "    Sb.sub.2 O.sub.3                                                                    "      "                                       98  "   CoO "    "    "    Mn.sub.2 O.sub.3                                                                    "      "                                       99  "   "   "    "    "    Sb.sub.2 O.sub.3                                                                    "      "                                       100 "   MnO "    "    "    Co.sub.2 O.sub.3                                                                    "      "                                       101 "   "   "    "    "    Sb.sub.2 O.sub.3                                                                    "      "                                       102 "   ZnO "    "    "    Mn.sub.2 O.sub.3                                                                    "      "                                       103 "   "   "    "    "    Co.sub.2 O.sub.3                                                                    "      "                                       104 "   "   "    "    "    Sb.sub.2 O.sub.3                                                                    "      "                                       105 NiO CoO "    "    "    Mn.sub.2 O.sub.3                                                                    "      "                                       106 "   "   "    "    "    Sb.sub.2 O.sub.3                                                                    "      "                                       107 "   MnO "    "    "    Co.sub.2 O.sub.3                                                                    "      "                                       108 "   "   "    "    "    Sb.sub.2 O.sub.3                                                                    "      "                                       109 "   ZnO "    "    "    Mn.sub.2 O.sub.3                                                                    "      "                                       110 "   "   "    "    "    Co.sub.2 O.sub.3                                                                    "      "                                       111 "   "   "    "    "    Sb.sub.2 O.sub.3                                                                    "      "                                       112 CoO MnO "    "    "    Sb.sub.2 O.sub.3                                                                    "      "                                       113 "   ZnO "    "    "    Mn.sub.2 O.sub.3                                                                    "      "                                       114 "   "   "    "    "    Sb.sub.2 O.sub.3                                                                    "      "                                       115 ZnO MnO "    "    "    Co.sub.2 O.sub.3                                                                    "      "                                       116 "   "   "    "    "    Sb.sub.2 O.sub.3                                                                    "      "                                       __________________________________________________________________________

                                      Table 7 (b)                                  __________________________________________________________________________                            Resistance deviation                                        Resistance (Ω)                                                                               R.sub.t -R.sub.o                                       Sample            B-value  × 100 (%)                                                            R.sub.o                                                 No.                    in the lapse                                                                          in the lapse                                         at 600°C                                                                       at 1000°C                                                                           of 100 hrs                                                                            of 1000 hrs                                      __________________________________________________________________________     95  4.6 × 10.sup.3                                                                  1.8 × 10.sup.2                                                                  9000 2.3    11                                               96  5.8 × 10.sup.3                                                                  2.2 × 10.sup.2                                                                  9100 1.7    8.3                                              97  2.9 × 10.sup.3                                                                  1.3 × 10.sup.2                                                                  8600 3.2    20                                               98  2.3 × 10.sup.3                                                                  1.2 × 10.sup.2                                                                  8200 3.3    24                                               99  3.2 × 10.sup.3                                                                  1.4 × 10.sup.2                                                                  8700 3.7    31                                               100 4.9 × 10.sup.4                                                                  7.2 × 10.sup.2                                                                  11700                                                                               4.5    37                                               101 2.1 × 10.sup.4                                                                  6.8 × 10.sup.2                                                                  9500 4.1    28                                               102 9.6 × 10.sup.2                                                                  1.1 × 10.sup.2                                                                  6000 5.6    46                                               103 6.0 × 10.sup. 3                                                                 2.5 × 10.sup.2                                                                  8800 2.0    9.4                                              104 4.2 × 10.sup.3                                                                  2.7 × 10.sup.2                                                                  7600 3.1    18                                               105 1.1 × 10.sup.3                                                                  7.9 × 10                                                                        7300 3.8    26                                               106 2.5 × 10.sup.3                                                                  1.2 × 10.sup.2                                                                  8400 4.3    33                                               107 5.8 × 10.sup.3                                                                  2.4 × 10.sup.2                                                                  8900 3.0    22                                               108 1.1 × 10.sup.4                                                                  5.2 × 10.sup.2                                                                  8500 4.2    35                                               109 9.3 × 10.sup.2                                                                  1.0 × 10.sup.2                                                                  6200 5.4    47                                               110 3.8 × 10.sup.3                                                                  1.6 × 10.sup.2                                                                  8800 2.6    18                                               111 2.3 × 10.sup.3                                                                  1.4 × 10.sup.2                                                                  7800 4.9    35                                               112 1.8 × 10.sup.3                                                                  8.7 × 10                                                                        8400 5.1    43                                               113 8.6 × 10.sup.2                                                                  9.7 × 10                                                                        6100 3.6    29                                               114 9.7 × 10.sup.2                                                                  9.8 × 10                                                                        6400 4.2    34                                               115 4.6 × 10.sup.3                                                                  1.8 × 10.sup.2                                                                  9000 2.8    21                                               116 3.8 × 10.sup.3                                                                  1.6 × 10.sup.2                                                                  8800 3.1    27                                               __________________________________________________________________________

EXAMPLE 8

High temperature thermistors of compositions listed in Table 8(a) were prepared in a manner similar to that of Example 1.

For each sample of the resultant thermistors, the measured electrical characteristics are given in Table 8(b).

                                      Table 8(a)                                   __________________________________________________________________________     Compositions (ingredient)(mol ratio)                                                                               Prefiring                                                                             Sintering                           Sample                              temperature                                                                           temperature                         No. 0.4 0.3 0.3 0.3  0.5  0.1  0.1  (°C)                                                                           (°C)                         __________________________________________________________________________     117 MgO NiO CoO Al.sub.2 O.sub.3                                                                    Cr.sub.2 O.sub.3                                                                    Fe.sub.2 O.sub.3                                                                    Mn.sub.2 O.sub.3                                                                    1250   1640                                118 "   "   "   "    "    "    Sb.sub.2 O.sub.3                                                                    "      "                                   119 "   "   MnO "    "    "    Mn.sub.2 O.sub.3                                                                    "      1630                                120 "   "   "   "    "    "    Co.sub.2 O.sub.3                                                                    "      "                                   121 "   "   "   "    "    "    Sb.sub.2 O.sub.3                                                                    "      "                                   122 "   "   ZnO "    "    "    Mn.sub.2 O.sub.3                                                                    "      1640                                123 "   "   "   "    "    "    Co.sub.2 O.sub.3                                                                    "      "                                   124 "   "   "   "    "    "    Sb.sub.2 O.sub.3                                                                    "      "                                   125 NiO CoO MnO "    "    "    Co.sub.2 O.sub.3                                                                    "      1620                                126 "   "   "   "    "    "    Sb.sub.2 O.sub.3                                                                    "      "                                   127 "   "   ZnO "    "    "    Mn.sub.2 O.sub.3                                                                    "      "                                   128 "   "   "   "    "    "    Sb.sub.2 O.sub.3                                                                    "      "                                   __________________________________________________________________________

                                      Table 8(b)                                   __________________________________________________________________________                            Resistance deviation                                        Resistance (Ω)                                                                               R hd t- R.sub.o                                        Sample            B-value  × 100 (%)                                                            R.sub.o                                                 No.                    in the lapse                                                                          in the lapse                                         at 600°C                                                                       at 1000°C                                                                           of 100 hrs                                                                            of 1000 hrs                                      __________________________________________________________________________     117 3.2 × 10.sup.3                                                                  1.5 × 10.sup.2                                                                  8500 2.8    18                                               118 3.1 × 10.sup.3                                                                  1.4 × 10.sup.2                                                                  8600 3.5    25                                               119 1.3 × 10.sup.3                                                                  1.2 × 10.sup.2                                                                  6600 3.7    28                                               120 2.0 × 10.sup.4                                                                  4.1 × 10.sup.2                                                                  10800                                                                               2.0    14                                               121 6.7 × 10.sup.3                                                                  3.2 × 10.sup.2                                                                  8500 3.6    26                                               122 2.2 × 10.sup.3                                                                  1.4 × 10.sup.2                                                                  7700 3.1    25                                               123 5.9 × 10.sup.3                                                                  2.3 × 10.sup.2                                                                  9000 1.8    8.8                                              124 3.4 × 10.sup.3                                                                  2.0 × 10.sup.2                                                                  7900 3.1    19                                               125 7.7 ×  10.sup.3                                                                 2.3 × 10.sup.2                                                                  8900 2.8    17                                               126 5.2 × 10.sup.3                                                                  3.0 × 10.sup.2                                                                  7900 4.2    34                                               127 9.8 × 10.sup.2                                                                  9.6 × 10                                                                        6500 4.3    35                                               128 2.4 × 10.sup.3                                                                  1.3 × 10.sup.2                                                                  8100 4.6    34                                               __________________________________________________________________________

EXAMPLE 9

High temperature thermistors of compositions listed is Table 9(a) were prepared in a manner similar to that of Example 1.

For each sample of the resultant thermistors, the measured electrical characteristics are given in Table 9(b).

                                      Table 9(a)                                   __________________________________________________________________________     Sample                                                                             Compositions (mole ratio)                                                                               Prefiring                                                                             Sintering                                  No.                          temperature                                                                           temperature                                    MgO  NiO  Al.sub.2 O.sub.3                                                                    Cr.sub.2 O.sub.3                                                                    Fe.sub.2 O.sub.3                                                                    (°C)                                                                           (°C)                                __________________________________________________________________________     129 1.01 0    0.3  0.5  0.2  1250   1650                                       130 1.03 0    0.3  0.5  0.2  "      "                                          131 1.10 0    0.3  0.5  0.2  "      1670                                       132 1.25 0    0.3  0.5  0.2  "      "                                          133 1.10 0    0.5  0.25 0.25 "      1650                                       134 0    1.01 0.3  0.5  0.2  "      1620                                       135 0    1.05 0.3  0.5  0.2  "      "                                          136 0    1.25 0.3  0.5  0.2  "      1640                                       137 0.51 0.51 0.3  0.5  0.2  "      "                                          138 0.55 0.55 0.3  0.5  0.2  "      1650                                       139 0.625                                                                               0.625                                                                               0.3  0.5  0.2  "      1670                                       __________________________________________________________________________

                                      Table 9(b)                                   __________________________________________________________________________                            Resistance deviation                                                           R.sub.t - R.sub.o                                       Sample                                                                             Resistance (Ω)                                                                         B-value  × 100 (%)                                                            R.sub.o                                                 No.                    in the lapse                                                                          in the lapse                                         at 600°C                                                                       at 1000°C                                                                           of 100 hrs                                                                            of 1000 hrs                                      __________________________________________________________________________     129 6.3 × 10.sup.4                                                                  1.2 × 10.sup.3                                                                  11000                                                                               1.4    8.6                                              130 3.4 × 10.sup.4                                                                  8.3 × 10.sup.2                                                                  10300                                                                               3.5    23                                               131 5.0 × 10.sup.3                                                                  5.8 × 10.sup.2                                                                  6000 21     75                                               132 2.1 × 10.sup.3                                                                  4.7 × 10.sup.2                                                                  4200 82     410                                              133 1.2 × 10.sup.3                                                                  4.9 × 10.sup.2                                                                  2500 37     120                                              134 2.0 × 10.sup.4                                                                  2.8 × 10.sup.2                                                                  12000                                                                               1.4    4.3                                              135 6.6 × 10.sup.3                                                                  2.1 × 10.sup.2                                                                  9600 8.9    28                                               136 1.5 × 10.sup.3                                                                  1.4 × 10.sup.2                                                                  6600 72     300                                              137 3.9 × 10.sup. 3                                                                 1.7 × 10.sup.2                                                                  8700 0.8    7.3                                              138 1.8 × 10.sup.3                                                                  1.2 × 10.sup.2                                                                  7500 20     64                                               139 8.9 × 10.sup.2                                                                  1.1 × 10.sup.2                                                                  5800 65     270                                              __________________________________________________________________________

EXAMPLE 10

High temperature thermistors of compositions listed in Table 10(a) were prepared in a manner similar to that of Example 1.

For each sample of the resultant thermistors, the measured electrical characteristics are given in Table 10(b).

                                      Table 10(a)                                  __________________________________________________________________________     Sample                                                                             Compositions (mol ratio)    Prefiring                                                                             Sintering                               No.                             temperature                                                                           temperature                             MgO     NiO Al.sub.2 O.sub.3                                                                    Cr.sub.2 O.sub.3                                                                    Fe.sub.2 O.sub.3                                                                    Mn.sub.2 O.sub.3                                                                    (%)    (%)                                     __________________________________________________________________________     140 1.00                                                                               0   0.303                                                                               0.505                                                                               0.202                                                                               0    1250   1650                                    141 1.00                                                                               0   0.309                                                                               0.515                                                                               0.206                                                                               0    "      "                                       142 1.00                                                                               0   0.33 0.55 0.22 0    "      "                                       143 1.00                                                                               0   0.375                                                                               0.625                                                                               0.250                                                                               0    "      "                                       144 1.00                                                                               0   0.75 0.25 0.25 0    "      "                                       145 1.00                                                                               0   0.33 0.55 0    0.22 "      "                                       146 1.00                                                                               0   0.375                                                                               0.625                                                                               0    0.25 "      "                                       147 0.50                                                                               0.50                                                                               0.33 0.55 0.22 0    "      "                                       148 0.50                                                                               0.50                                                                               0.33 0.55 0.11 0.11 "      "                                       149 0.50                                                                               0.50                                                                               0.375                                                                               0.625                                                                               0.125                                                                               0.125                                                                               "      "                                       __________________________________________________________________________

                                      Table 10(b)                                  __________________________________________________________________________                            Resistance deviation                                                           R.sub.t - R.sub.o                                       Sample                                                                             Resistance (Ω)                                                                         B-value  × 100 (%)                                                            R.sub.o                                                 No.                    in the lapse                                                                          in the lapse                                         at 600°C                                                                       at 1000°C                                                                           of 100 hrs                                                                            of 1000 hrs                                      __________________________________________________________________________     140 4.4 × 10.sup.5                                                                  2.3 × 10.sup.3                                                                  14600                                                                               1.0    7.4                                              141 8.0 × 10.sup.5                                                                  3.1 × 10.sup.3                                                                  15400                                                                               3.8    18                                               142 2.0 × 10.sup.6                                                                  3.4 × 10.sup.3                                                                  17700                                                                               23     69                                               143 8.1 × 10.sup.6                                                                  4.7 × 10.sup.3                                                                  20700                                                                               76     320                                              144 2.1 × 10.sup.6                                                                  9.8 × 10.sup.3                                                                  14900                                                                               32     88                                               145 3.5 × 10.sup.4                                                                  1.1 × 10.sup.3                                                                  9600 18     56                                               146 8.0 × 10.sup.4                                                                  1.6 × 10.sup.3                                                                  10900                                                                               70     290                                              147 1.9 × 10.sup.4                                                                  3.1 × 10.sup.2                                                                  11400                                                                               15     54                                               148 2.3 × 10.sup.4                                                                  2.5 × 10.sup.2                                                                  12600                                                                               20     61                                               149 5.7 × 10.sup.4                                                                  3.7 × 10.sup.2                                                                  14000                                                                               73     310                                              __________________________________________________________________________

All of the thermistors which have the compositions in accordance with the present invention show that their resistance deviation ##EQU3## in the lapse of 100 hours under an application of d.c. 6V is smaller than 100%. All of these samples can be used in the working temperature of lower than 700°C. Especially, the samples, which show resistance deviation of smaller than 100% in the lapse of 1000 hours under an application of d.c. 6V, can be used in the working temperature of lower than 1000°C. Furthermore, the samples, which show resistance deviation of smaller than 10% in the lapse of 1000 hours under an application of d.c. 6V, are suitable for use in the working temperature of lower than 1300°C. 

What is claimed is:
 1. A high temperature thermistor composition comprising a spinel-type solid solution having the chemical formula of (Mg.sub.[_(p).sbsb.1_(]Ni).sub.[_(p).sbsb.2_(]Co).sub.[_(p).sbsb.3_(]Mn).sub.[_(p).sbsb.4_(]Zn).sub.[_(p).sbsb.5_(])) (Al.sub.[ _(x) _(]Cr).sub.[_(y) _(]Fe) .sub.[_(z).sbsb.1_(]Mn).sub.[_(z).sbsb.2_(]Co).sub.[_(z).sbsb.3.sub.]Sb.sub.[_(z).sbsb.4_(]))₂ O₄, wherein p₁ +p₂ +p₃ +p₄ +p₅ =1, 0≦p_(n) ≦1 (n=1, 2, 3, 4, 5), z₁ +z₂ +z₃ +z₄ =z, x+y+z=1, 0.005≦x≦0.80, 0.03≦y≦0.95, 0.005≦z≦0.70 and 0≦z_(n) ≦0.70 (n=1,2,3,4).
 2. A high temperature thermistor composition as claimed in claim 1, wherein said spinel-type solid solution having a chemical formula of A (Al_(x) Cr_(y) B_(z))₂ O₄ wherein A stands for a metal selected from the group consisting of Mg, Ni, Co, Mn and Zn, and B stands for a metal selected from the group consisting of Fe, Mn, Co and Sb, and x ranges from 0.005 to 0.80, y ranges from 0.03 to 0.95, z ranges from 0.005 to 0.70, and the sum of x, y and z is unity.
 3. A high temperature thermistor composition as claimed in claim 1, wherein said spinel-type solid solution in a chemical formula of (Mg_(1-p) A_(p))(Al_(x) Cr_(y) B_(z))₂ O₄ wherein A stands for a metal selected from the group consisting of Ni, Co, Mn and Zn, and B stands for a metal selected from the group consisting of Fe, Mn, Co and Sb, and p ranges from 0.001 to 0.999, x ranges from 0.005 to 0.80, y ranges from 0.03 to 0.95, z ranges from 0.005 to 0.70, and the sum of x, y and z is unity.
 4. A high temperature thermistor composition as claimed in claim 1, wherein said spinel-type solid solution in a chemical formula of (Ni_(1-p) A_(p))(Al.sub. x Cr_(y) B_(z))₂ O₄ wherein A stands for a metal selected from the group consisting of Co, Mn and Zn, and B stands for metal selected from the group consisting of Fe, Mn, Co and Sb, and p ranges from 0.001 to 0.999, x ranges from 0.005 to 0.80, y ranges from 0.03 to 0.95, z ranges from 0.005 to 0.70, and the sum of x, y and z is unity.
 5. A high temperature thermistor composition as claimed in claim 1, wherein said spinel-type solid solution in a chemical formula of (Co_(1-p) A_(p))(Al.sub. x Cr_(y) B_(z))₂ O₄ wherein A stands for a metal selected from the group consisting of Mn and Zn, and B stands for a metal selected from the group consisting of Fe, Mn, Co and Sb, and p ranges from 0.001 to 0.999, x ranges from 0.005 to 0.80, y ranges from 0.03 to 0.95, z ranges from 0.005 to 0.70 and the sum of x, y and z is unity.
 6. A high temperature thermistor composition as claimed in claim 1, wherein said spinel-type solid solution in a chemical formula of (Zn.sub.[₁ _(-p) _(]Mn).sub.[31 _(p) _(]))(Al.sub.[_(x) _(]Cr).sub.[_(y) _(]B).sub.[_(z) _(]))₂ O₄ wherein B stands for a metal selected from the group consisting of Fe, Mn, Co and Sb, and p ranges from 0.001 to 0.999, x ranges from 0.005 to 0.80, y ranges from 0.03 to 0.95, z ranges from 0.005 to 0.70, and the sum of x, y and z is unity.
 7. A high temperature thermistor compositon as claimed in claim 1, wherein said spinel-type solid solution in a chemical formula of (Mg₁ _(-p) _(-q) Ni_(p) A_(q))(Al.sub. x Cr_(y) B_(z))₂ O₄ wherein A stands for a metal selected from the group consisting of Co, Mn and Zn, and B stands for a metal selected from the group consisting of Fe, Mn, Co and Sb, and p ranges from 0.001 to 0.999, q ranges from 0.0005 to 0.998, the sum of p and q is smaller than unity, x ranges from 0.005 to 0.80, y ranges from 0.03 to 0.95, z ranges from 0.005 to 0.70, and the sum of x, y and z is unity.
 8. A high temperature thermistor composition as claimed in claim 1, wherein said spinel-type solid solution in a chemical formula of (Ni₁ _(-p) _(-q) Co_(p) A_(g))(Al.sub. x Cr_(y) B_(z))₂ O₄ wherein A stands for a metal selected from the group consisting of Mn and Zn, B stands for a metal selected from the group consisting of Fe, Mn, Co and Sb, and p ranges from 0.001 to 0.999, q ranges from 0.0005 to 0.998, the sum of p and q is smaller than unity, x ranges from 0.005 to 0.80, y ranges from 0.03 to 0.95, z ranges from 0.005 to 0.70, and the sum of x, y and z is unity.
 9. A high temperature thermistor composition as claimed in claim 1, wherein said spinel-type solid solution in a chemical formula of A (Al_(x) Cr_(y) Fe_(z) _(-w) B_(w))₂ O₄ wherein A stands for a metal selected from the group consisting of Mg, Ni, Co, Mn and Zn, B stands for a metal selected from the group consisting of Mn, Co and Sb, and x ranges from 0.005 to 0.80, y ranges from 0.03 to 0.95, z ranges from 0.005 to 0.70, w ranges from 0.001 to 0.699, and the sum of x, y and z is unity.
 10. A high temperature thermistor composition as claimed in claim 1, wherein said spinel-type solid solution in a chemical formula of (Mg₁ _(-p) A_(p))(Al.sub. x Cr_(y) Fe_(z) _(-w) B_(w))₂ O.sub. 4 wherein A stands for )(Al_(metal) selected from the group consisting of Ni, Co, Mn and Zn, B stands for a metal selected from the group consisting of Mn, Co and Sb, and p ranges from 0.001 to 0.999, x ranges from 0.005 to 0.80, y ranges from 0.03 to 0.95, z ranges from 0.005 to 0.70, w ranges from 0.001 to 0.669 and the sum of x, y and z is unity.
 11. A high temperature thermistor composition as claimed in claim 1, where in said spinel-type solid solution in a chemical formula of (Ni₁ _(-p) A_(p) ()Al.sub. x Cr_(y) Fe_(z) _(-w) B.sub. w)₂ O₄ wherein A stands for a metal selected from the group consisting of Co, Mn and Zn, B stands for a metal selected from the group consisting of Mn, Co and Sb, and p ranges from 0.001 to 0.999 x ranges 0.005 to 0.80, y ranges from 0.03 to 0.95, z ranges from 0.005 to 0.70, w ranges from 0.001 to 0.699, and the sum of x, y and z is unity.
 12. A high temperature thermistor composition as claimed in claim 1, wherein said spinel-type solid solution in a chemical formula of (Co₁ _(-p) A_(p))(Al.sub. x Cr_(y) Fe_(z) _(-w) B_(w)).sub. 2 O₄ wherein A stands for a metal selected from the group consisting of Mn and Zn, B stands for a metal selected from the group consisting of Mn, Co and Sb and p ranges from 0.001 to 0.999, x ranges 0.005 to 0.80, y ranges from 0.03 to 0.95, z ranges from 0.005 to 0.70, w ranges from 0.001 to 0.699, and the sum of x, y and z is unity.
 13. A high temperature thermistor composition as claimed in claim 1, wherein said spinel-type solid solution in a chemical formula of (Zn₁ _(-p) Mn_(p))(Al.sub. x Cr_(y) Fe_(z) _(-w) B_(w))₂ O₄ wherein B stands for a metal selected from the group consisting of Mn, Co and Sb and p ranges from 0.001 to 0.999, x ranges from 0.005 to 0.80, y ranges from 0.03 to 0.95, z ranges form 0.005 to 0.70, w ranges from 0.001 to 0.699, and the sum of x, y and z is unity.
 14. A high temperature thermistor composition as claimed in claim 1, wherein said spinel-type solid solution in a chemical formula of (Mg₁ _(-p) _(-q) Ni_(p) A_(q))(Al.sub. x Cr_(y) Fe_(z) _(-w) B_(w))₂ O₄ wherein A stands for a metal selected from the group consisting of Co, Mn and Zn, B stands for a metal selected from the group consisting of Mn, Co and Sb, and p ranges from 0.001 to 0.999, q ranges from 0.0005 to 0.998, the sum of p and q is smaller than unity, x ranges from 0.005 to 0.80, y ranges from 0.03 to 0.95, z ranges from 0.005 to 0.70, w ranges from 0.001 to 0.699, and the sum of x, y and z is unity.
 15. A high temperture thermistor composition as claimed in claim 1, wherein said spinel-type solid solution in a chemical formula of (Nil.sub._(-p) _(-q) Co_(p) A_(g))(Al.sub. x Cr_(y) Fe_(z) _(-w) B_(w))₂ O₄ wherein A stands for a metal selected from the group consisting of, Mn and Zn, B stands for a metal selected from the group consisting of Mn, Co and Sb, and p ranges from 0.001 to 0.999, q ranges from 0.0005 to 0.998, the sum of p and q is smaller than unity, x ranges from 0.005 to 0.80, y ranges from 0.03 to 0.95, z ranges from 0.005 to 0.70, w ranges from 0.001 to 0.699, and the sum of x, y and z is unity.
 16. A high temperature themistor composition comprising more than 80 molar percent of a spinel-type solid solution in a chemical formula of A (Al_(x) Cr_(y) B_(z))₂ O₄ and less than 20 molar percent of an oxide in a chemical formula of AO, wherein A stands for metal selected from the group consisting of Mg, Ni, Co, Mn and Zn, and B stands for a metal selected from the group consisting of Fe, Mn, Co and Sb, and x ranges from 0.005 to 0.80, y ranges from 0.03 to 0.95, z ranges from 0.005 to 0.70, and the sum of x, y and z is unity.
 17. A high temperature thermistor composition comprising more than 80 molar percent of a spinel-type solid solution in a chemical formula of A (Al_(x) Cr_(y) B_(z))₂ O₄ and less than 20 molar percent in the sum of the amounts of Al₂ O₃, Cr₂ O₃ and an oxide in a chemical formula of B₂ O₃ which are in a molar fraction of x, y and z, respectively, wherein A stands for a metal selected from the group consisting of Mg, Ni, Co, Mn and Zn, and B stands for a metal selected from the group consisting of Fe Mn, Co and Sb, and x ranges from 0.005 to 0.80, y ranges from 0.03 to 0.95, z ranges from 0.005 to 0.70, and the sum of x, y and z is unity.
 18. A high temperature thermistor composition comprising more than 80 molar percent of a spinel-type solid solution in a chemical formula of (Mg₁ _(-p) A_(p))(Al.sub. x Cr_(y) B_(z))₂ O₄ and less than 20 molar percent in the sum of the amounts of MgO and an oxide in a chemical formula of AO which are in a molar fraction of 1-p and p, respectively, wherein A stands for a metal selected from the group consisting of Mg, Ni, Co, Mn and Zn, and B stands for a metal selected from the group consisting of Fe, Mn, Co and Sb, and p ranges from 0.001 to 0.999, x ranges from 0.005 to 0.80, y ranges form 0.03 to 0.95 z ranges from 0.005 to 0.70, and the sum of x, y and z is unity.
 19. A high temperature thermistor composition comprising more than 80 molar percent of a spinel-type solid solution in a chemical formula of (Mg₁ _(-p) A_(p))(Al.sub. x Cr_(y) B_(z))₂ O₄ and less than 20 molar percent in the sum of the amounts of Al₂ O₃, Cr₂ O₃ and an oxide in a chemical formula of B₂ O₃ which are in a molar fraction of x, y and z, respectively, wherein A stands for a metal selected from the group consisting of Mg, Ni, Co, Mn and Zn, and B stands for a metal selected from the group consisting of Fe, Mn, Co and Sb, and p ranges from 0.001 to 0.999, x ranges from 0.005 to 0.80, y ranges from 0.03 to 0.95, z ranges from 0.005 to 0.70, and the sum of x, y and z is unity. 